Fuel cell systems are emerging as a promising energy source for mobile and power generation applications due to their high efficiency, high reliability and low emissions of regulated pollutants. Fuel cell systems require an electrical isolation between the low-voltage output of the fuel cell stack and the high-voltage dc bus for protection. High-frequency-link (HFL) power converters are therefore being widely applied in fuel cell systems because they provide high-frequency galvanic isolation and provide a large reduction in the size and weight of the isolation transformer.
One of the key issues in fuel cell systems is that the fuel cell current low-frequency ripple exhibits a hysteresis behavior and results a thermal issue among the fuel cell stacks. A straight-forward solution is to incorporate a bulky electrolytic capacitor as the energy buffer to reduce the ripple current. However, the use of an electrolytic capacitor will decrease the system lifetime as well as increase the system volume and cost. Therefore, being able to suppress the low-frequency ripple without using electrolytic capacitors is crucial to the future of fuel cell systems.
Accordingly, what is needed in the art is a current-fed, three-phase, high-frequency-link fuel cell having a reduced low-frequency ripple current that does not require the use of electrolytic capacitors. However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.